Concrete can be one of the most durable building materials and structures made of concrete can have a long service life. Concrete is a composite construction material composed primarily of aggregate, cement, and water. It provides superior fire resistance, compared with wooden construction and can gain strength over time. Further, as it is used as liquid that subsequently hardens it can be formed into complex geometries and may poured either directly into formworks at the construction sites (so called ready mix concrete) or employed remotely to pre-build concrete elements and structures. Overall concrete is the most widely used construction material in the world with an annual consumption estimated at approximately 30 billion tons in 2006, compared to 2 billion in 1950. During the next 5 years concrete consumption is estimated to grow with a Compound Annual Growth Rate (CAGR) between 6% and 9% according to market forecasts of cement and concrete admixtures globally over the period 2012 to 2017 such that the 30 billion ton consumption will increase to approximately 40 billion tons.
Concrete is widely used for making architectural structures, foundations, brick/block walls, pavements, bridges/overpasses, motorways/roads, runways, parking structures, dams, pools/reservoirs, pipes, footings for gates, fences and poles and even boats. Reinforced concrete, pre-stressed concrete and precast concrete are the most widely used types of concrete functional extensions. Concrete is strong in compression, as the aggregate efficiently carries the compression load. However, it is weak in tension as the cement holding the aggregate in place can crack, allowing the structure to fail. Reinforced concrete solves these problems by adding steel reinforcing bars, steel fibers, glass fiber, or plastic fiber to carry tensile loads. Thereafter the concrete is reinforced to withstand the tensile loads upon it. Due to their low cost and wide availability steel reinforcing bar (commonly referred to as rebar) has been the dominant reinforcing material for the past 50 years. However, these steel rebars may corrode whereby the oxidation products (rust) expand and tend to flake, thereby cracking the concrete and reducing the bonding between the rebar and the concrete. Such corrosion may arise from several sources including carbonation when the surface of concrete is exposed to high concentration of carbon dioxide or chlorides, such as when the concrete structure is in contact with a chloride-contaminated environment such as arises with de-icing salts and marine environment.
Just as the exploitation of concrete increased over the past 50 years then so have the requirements on it as engineering structures continue to push new boundaries of higher buildings, longer bridges, larger dams, artificial islands etc. Further disasters with poor concrete etc. have led to stricter regulation and compliance requirements. Accordingly, today the concrete industry faces competing demands for faster construction, shorter durations of formwork use, cost reductions whilst ensuring safety and quality are met or exceeded. As such testing techniques for concrete have evolved and will continue to evolve to meet these requirements. However, many of these techniques require samples be taken, full extended curing of the concrete performed, or simple mechanical tests be performed on site with the concrete being delivered.
However, it would be beneficial to provide concrete suppliers, construction companies, regulators, architects, and others requiring data regarding the cure, performance, corrosion of concrete at different points in its life cycle with a series of simple electrical tests that removed subjectivity, allowed for rapid assessment, were integrable to the construction process, and provided full life cycle assessment.
Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.